1. Technical Field
The present invention relates to a vehicle wheel suspension system, and is particularly directed to a lower control arm for use in a vehicle wheel suspension system.
2. Background Art
Lower control arms for use in a vehicle wheel suspension system are known. A typical lower control arm comprises (i) a ball Joint to which a steering knuckle is pivotably connected, and (ii) at least one rubber bushing which is connectable to a vehicle frame part of the vehicle.
There are a number of disadvantages in using a rubber bushing in a typical lower control arm. One disadvantage is that the spring rate and damping rate of the rubber bushing change as the rubber material of the rubber bushing ages and/or is attacked by chemicals. When this occurs, the overall vehicle spring and damping rate is affected which, in turn, affects vehicle ride and handling.
Another disadvantage is that the rubber material of the rubber bushing is deflectable. If the rubber material deflects, the lower control arm deflects. The amount of deflection may be as high as 0.25 inches. If the lower control arm deflects, both vehicle static wheel alignment and vehicle dynamic wheel alignment are affected which may cause imprecise and/or unstable handling characteristics.
Still another disadvantage is that the rubber bushing makes noises as relative movement occurs between the rubber bushing and mating steel parts. Also, the rubber bushing has relatively high internal friction. Due to the relatively high internal friction of the rubber bushing, some vibrations and loads are transmitted through the rubber bushing before suspension compliance can eliminate them.